php, 52 bytes

Result

WA

Code [DL]

<?=($a=str_split(readline()))|sort($a)?implode($a)?>

stdin

9993871224356339087844751908048817401061119419941706420305584016372374863846165946635275360820655555

stdout

stderr

PHP Parse error:  syntax error, unexpected '?>' in /volume/CODE on line 1

strace